The Torah reading for the first day of Shavuot describes the Giving of the Torah at Mount Sinai which occurred on this day, where G‑d revealed Himself to the Children of Israel, entered into an eternal covenant with them, communicated to the them Ten Commandments, and summoned Moses to the top of the mountain to receive the Torah

In the third month following the children of Israel's exodus from the land of Egypt; that same day they came into the wilderness of Sinai... and there Israel camped opposite the mountain.

Moses is summoned to the top of Mount Sinai, where G‑d tells him that He is taking the children of Israel as His own chosen nation:

"Thus shall you say to the house of Jacob, and tell the children of Israel:

"You have seen what I did to Egypt, and how I bore you on eagles' wings, and brought you to Myself. Now therefore, if you will indeed obey My voice, and keep My covenant, you shall be My own treasure from among all peoples, for all the earth is Mine

"And you shall be to Me a kingdom of priests, and a holy nation."

Moses descends from the mountain and "called for the elders of the people, and laid before them all these words which G‑d had commanded him."

And all the people answered together, and said: "All that G‑d has spoken we will do." And Moses reported the words of the people to G‑d.

G‑d instructs that the people should purify and sanctify themselves for two days, "Because on the third day G‑d shall descend upon Mount Sinai before the eyes of the entire people." The mountain itself should be fenced in, and all should be warned against ascending the mountain or even "touching its edge."

The Revelation

And it came to pass on the third day when it was morning, that there were thunders and lightnings, and a thick cloud upon the mountain, and the sound of a shofar exceeding loud; so that all the people in the camp trembled.

Moses brought the people out of the camp to meet with G‑d; and they stood under the mountain.

And Mount Sinai smoked in every part, because G‑d descended upon it in fire: and the smoke of it ascended like the smoke of a furnace, and the whole mountain quaked greatly.

The voice of the shofar sounded louder and louder; Moses speaks, and G‑d answers him by a voice.

And G‑d came down upon Mount Sinai, on the top of the mountain. And G‑d called Moses up to the top of the mount; and Moses went up....

The Ten Commandments

And G‑d spoke all these words, saying:

I am G‑d your G‑d, who has brought you out of the land of Egypt, out of the house of bondage.

You shall have no other gods beside Me. You shall not make for yourself any carved idol, or any likeness of any thing... you shall not bow down to them, nor serve them...

You shall not take the name of G‑d your G‑d in vain...

Remember the Sabbath day, to keep it holy. Six days shall you labor, and do all your work; but the seventh day is a sabbath to G‑d... For in six days G‑d made heaven and earth, the sea, and all that is in them, and rested on the seventh day. Therefore G‑d blessed the Sabbath day, and hallowed it.

Honor your father and your mother...

You shall not murder.

You shall not commit adultery.

You shall not steal.

You shall not bear false witness against your fellow.

You shall not covet... anything that is your fellow's.

The people are overwhelmed by all that they see and hear, and beg Moses: "You speak with us, and we shall hear; but let not G‑d speak with us, lest we die." So "the people stood afar off, and Moses drew near to the thick darkness where G‑d was."

The reading concludes with a number of additional laws communicated at Sinai, including the prohibition to use any iron tools in constructing an altar to G‑d.

Pilgrimage

On the second day of Shavuot we read from Deuteronomy chapters 14-16, which detail the laws of the three pilgrimage festivals—Passover, Shavuot and Sukkot—on which all Jews came "to see and be seen before the face of G‑d" in the Holy Temple in Jerusalem. The reading also includes the laws of tithing, the sabbatical year, charity and the consecration of firstborn animals.